Method and apparatus for forming a head of a fastener

Abstract: A method and apparatus for forming a head (12) having a controlled pre-determined shape on an end of an elongate member (14), such as a wire, which is subsequently formed into a fastener. A portion of the wire (14) is secured in a pre-determined position and an end portion (22) is axially compressed to radially, outwardly expand it to form the head (12). Material flow is directed and controlled during axial compression, for example by flow control channels (30), to provide a controlled pre-determined shape for the head (12).

Description: This invention relates generally to a method and apparatus for forming a head for a fastener, and more particularly to a method and apparatus for axially compressing an end portion of a wire to outwardly expand a predetermined amount of wire material to form the head on the wire. Typically, to form a fastener such as a nail, an end portion of a wire is axially compressed with a punch or the like with sufficient force to radially outwardly expand the end portion of the wire to form a head thereon. The opposite end of the wire then is formed into a point to provide the finished nail. During axial compression of the wire, the wire material tends to randomly outwardly expand without control. This random expansion typically results in a nail head that is slightly out of round and/or off-centre with respect to the central axis of the wire shank, as illustrated in FIG. 6. Such a nail can be a problem when utilized in a power nailer causing tumbling or jamming of the nails therein. From FR-A-2403844 a method according to the preamble of claim 1 and an apparatus according to the preamble of claim 4 are known. According to a first aspect of this invention a method of forming a head on an elongate member comprises the features of claim 1. According to a second aspect of this invention an apparatus for forming a head on an elongate member, comprises the features of claim 4. Particular examples of a method, apparatus and resulting fasteners will now be described and contrasted with the prior art with reference to the accompanying drawings, in which:- FIG. 1 is a perspective view, in partial section, of a head forming punch of the invention and an end portion of a wire before punching; FIG. 2 is a perspective view, in partial section, of the head forming punch of the invention after a punching operation illustrating the head formed on the wire; FIG. 3 is an enlarged side elevational view of an end of a wire captured within a holding die, illustrated in partial section, prior to punching with the punch of the invention; FIG. 4 is a top plan view of the end portion of the wire and die taken along line 4-4 of FIG. 3 illustrating a ridge of material typically included on the end of the wire before punching; FIG. 5 is a top plan view of the head forming punch taken along line 5-5 of FIG. 3 illustrating the flow control channels thereof with the end portion of the wire in dotted outline illustrating the position of the wire with respect to the punch before punching; FIG. 6 is a top plan view of a prior art nail having a head formed without controlling the flow of wire material; FIG. 7 is a top plan view of a nail having a head formed by the method and apparatus of the invention illustrating the substantially circular and centred head; FIG. 8 is a side elevational view, in partial section, of the nail of FIG. 7; and, FIG. 9 is a bottom plan view of a nail head made by another embodiment of the method of the invention having flow control ribs on the underside of the nail head. Referring to FIG. 2, the apparatus of the invention generally is illustrated with the reference numeral 10. The apparatus 10 preferably forms a head 12 on a wire 14 with a head forming punch 16 and is typically utilized in manufacturing fasteners, such as nails or the like. Briefly, as FIGS. 2 and 3 illustrate, to form a nail, the wire 14 is provided from stock and typically is captured between a pair of holding dies 18 and 20 with an end portion 22 of the wire 14 protruding therefrom. The punch 16 is positioned adjacent to the end portion 22 to contact and axially compress the end portion 22 to form the head 12 by forcing radial, outward expansion of the material of the wire 14. To provide a shank 24 on the nail, the wire 14 is cut with a cutting tool (not illustrated) which is positioned on the side of the dies 18 and 20 opposite the punch 16. The cutting tool cuts and forms a pointed end (not illustrated) on the end of the now cut wire segment opposite the head 12 to complete the nail forming operation. When formed in this way, a stub or ridge 26 of wire material is provided on the end portion 22 of the wire 14, as illustrated in FIG. 3, and extends substantially across the entire width or diameter of the wire 14 and forms an edge thereon. The size and shape of the ridge 26 depends on the type of cutting tool utilized. As FIG. 7 illustrates, the head 12 typically formed by the method and apparatus of the invention is substantially circular in shape with a pre-determined thickness and is centred with respect to a central axis of the wire 14. It is to be noted that the particular shape and dimensions of the head 12 can vary. The head 12 also preferably includes a plurality of ribs 28 which are formed by the punch 16 as described in detail below. As FIGS. 7 and 8 illustrate, the ribs 28 are elongated, have a substantially semi-circular outer surface and extend across the entire diameter of the head 12. Preferably, the ribs 28 have a height which can vary between .001 to .015 inches (.0254 to .381 mm) and are spaced approximately 0.065 inches (1.651 mm) apart. It is to be noted, however, that the particular geometry and spacing of the ribs 28 can vary. The wire 14 preferably is made of a steel or other metal, is substantially circular in cross-section and can be plated for corrosion resistance, preferably with zinc. The particular material shape, size and coating of the wire 14, however, can vary. As FIG. 1 illustrates, to control and direct the outward flow of wire material during axial compression the punch 16 includes a plurality of flow control channels 30. The channels 30 preferably are semi-circular in cross-sectional configuration and extend into a face 32 of the punch 16 a pre-determined distance, which can vary. Although the desired flow control can be obtained with only one flow control channel 30, three flow control channels 30 preferably are utilized and are positioned substantially parallel to each other and extend across the entire width of the face 32. While three channels 30 are illustrated, the number, size and shape of the channels 30 can vary. As FIG. 2 illustrates, the punch 16 axially contacts and compresses the wire 14 in the direction of arrow "A". The size of the head 12 may vary and depends upon a number of factors such as the extent to which the end portion 22 protrudes from the holding dies 18 and 20, the velocity and force of the punch 16 and the material of the wire 14, among other factors. As FIG. 5 illustrates, the channels 30 of the punch 16 preferably are positioned during compression parallel with respect to the end portion 22 and the ridge 26 which are illustrated in dotted outline. The channels 30 also can be positioned at an angle with respect to the ridge 26 which can vary between 0° to 90° so long as the desired results are obtained as described herein. In operation, as FIG. 3 illustrates, the punch 16 axially contacts the end portion 22 of the wire 14 with a pre-determined force. The punch 16 axially compresses the end portion 22 and forces radial, outward expansion of the end portion 22 of the wire 14 to form a head 12 as illustrated in FIG. 2. During formation of the head 12, material of the wire 14 is directed along the flow control channels 30 of the punch 16 resulting in a pre-determined consistent shape with the head 12 substantially being centred with respect to the longitudinal axis of the wire 14. The head 12 and the shank 24 thereafter are cut from the remainder of the wire 14 to form a fastener. As FIG. 4 illustrates, the dimensions of the wire 14 and the holding dies 18 and 20 preferably are selected to provide a tight fit there-between with the dies 18 and 20 contacting along an interface 36. The holding dies 18 and 20 can include some type of gripper teeth (not illustrated) which can provide slight marks on the nails. The gripper marks, however, do not materially affect the forming or performance of the nail. Preferably, the punch 16 is moved into engagement with the end portion 22 which is stationary. The punch 16, however, may be stationary and the end portion 22 can be moved into engagement with the punch 16 if desired. FIG. 9 illustrates another nail 10b made by the method of the present invention where similar elements are identified by the same reference numerals. In this embodiment, straight ribs 28b are provided on the bottom of the head 12 similar to ribs 28. The ribs 28b are provided by the dies 18 and 20 which include corresponding flow control channels (not illustrated). In either event, the number, shape and dimensions of the ribs 28a or 28b can vary as desired to accommodate different head and shank diameters.

Claims: A method of forming a head (12) on an elongate member (14), by holding the elongate member (14) at a predetermined position and axially compressing an end portion (22,26) of the elongate member (14) to radially, outwardly expand the end portion (22, 26) by a punch (16) against a die (18,20), characterised in that the end portion (22,26) initially has a raised ridge of material (26), at least one of the punch (16) and die (18,20) including a linear channel (30) to control the amount and direction of the flow of material of the elongate member (14) and arranged at a predetermined angle relative to the raised ridge of material (26) to form the head (12) centred substantially on the longitudinal axis of the elongate member (14) and with a circular shape. A method according to claim 1, in which said at least one of the punch (16) and die (18,20) includes a plurality of generally parallel linear channels (30). A method according to claim 1 or 2, in which the or each linear channel (30) is arranged generally in parallel to the ridge (26) during the axial compression. An apparatus for forming a head (12) on an elongate member (14), a holding means for holding the elongate member (14) at a predetermined position, a punch (16) for axially compressing an end portion (22,26) of the elongate member (14) to radially, outwardly expand the end portion (22,26) and a die (18,20) against which the expanded end portion (22,26) is pressed characterised in that the apparatus further comprises a cutter for cutting the elongate member (14) and forming a raised ridge (26) on the cut end, and in that at least one of the punch (16) and die (18,20) includes a linear channel (30) to control the amount and direction of the flow of material of the elongate member (14) to form the head (12) centred substantially on the longitudinal axis of the elongate member (14) and with a circular shape, said at least one of the punch (16) and die (18,20) being so arranged that the linear channel (30) is at a predetermined angle with respect to the raised ridge (26) formed on the elongate member (14). An apparatus as defined in claim 4, in which said at least one of the punch (16) and die (18,20) includes a plurality of generally parallel linear channels (30).

Inventors: BINDER JOHN, GABRIEL WILLIAM, SCHNIEDERMEIER HENRY, SHELTON LAWRENCE, SYGNATOR HENRY, BINDER, JOHN, GABRIEL, WILLIAM, SCHNIEDERMEIER, HENRY, SHELTON, LAWRENCE, SYGNATOR, HENRY
Applicants: ILLINOIS TOOL WORKS, ILLINOIS TOOL WORKS INC.
Application year: 1994
Main classification: B21G3
IPC codes: B21J15, F16B15, B21G3, B21K1